what is the expected broaching force and max allowable broaching force?
Broaching refers to the use of a special broach to cut a very thin metal layer from the workpiece in turn, so that the surface can achieve high dimensional accuracy and low roughness. It is a high-efficiency processing method. When broaching a metal workpiece, the force required by the tool to cut into the workpiece and deform the material to be processed into chips is called broaching force. With the continuous wear of the broach blade, it is necessary to increase the cutting force gradually, but after the increase to a certain extent, the broach will be damaged, or the broach will be stopped during the cutting process due to poor maintenance status of the broaching machine. The safety load is the maximum allowable broaching force to prevent the above situation. To calculate the expected broaching force and max allowable broaching force, we need the below equation and diagram:
Calculation Equation and Diagram
Expected Broaching Force(Kgf)=Cutting Width(mm) X Cutting Depth Per Tooth(mm) X Cutting resistance Per Unit Area(Kgf.mm2) X Number of Simultaneous Cutting Teeth
Max Allowable Broaching Force(Kgf)=1.8 X Expected Broaching Force(Kgf)
Broaching Force Calculation Diagram
* | Cutting Depth Per Tooth(µm) | Cutting Depth Per Tooth(µm) | Cutting Depth Per Tooth(µm) | * |
Material | Round Broach | Spline Broach | Surface Broach | Cutting resistance Per Unit Area(Kgf.mm2) |
Alloy Steel | 10~20 | 25~30 | 30~70 | 300`400 |
Steel | 10~20 | 25~35 | 30~70 | 300 |
Cast Iron | 25~40 | 25~40 | 50·75 | 200 |
Malleable Cast Iron | 25~35 | 25~35 | 50·75 | 150~200 |
Light Alloy Metal | 25~35 | 30~40 | 60~100 | 100~200 |
Example of Calculation
Spline broach:Ø20 X Ø16 X 4 X NT6
Heat Resisting Steel Material
Cutting Lenght=25mm
Pitch=7.5mm
The number of simultaneous teeth=25/7.5=3.3≈4
Cutting depth per tooth=25µm
Expected Broaching Force=(4 X 6) X 0.025 X 0.4 X 4=1 Ton
Max Allowable Broaching Force=1 X 1.8=1.8 Ton
The Relation Between Broach Tool Lenght And Broaching Machine Stroke
Broach length is limited by the broaching machine stroke and jig/fixture
Broach Cutter Teeth Length+Length of rear end shank(Max)=Max Stroke-Cutting Length
Necessary Stroke=Teeth Length+Length of Rear End Shank(Max)+Broach Length＜Max Broaching Machine Stroke